The present invention relates to a thermal ink-transfer printer, in which an ink donor sheet is placed upon printing paper, and the ink attached to the ink donor sheet is transferred to the printing paper by supplying heat from a thermal head to the ink donor sheet.
Conventional printers, Xerographic apparatuses, and others are provided with a jam detecting device, to prevent a paper transporting path from being jammed with paper.
One of conventional jam detecting devices, as described in, for example, Japanese patent Publication (JP-B) No. 56-45787, includes a mechanical switch disposed in a printing-paper transporting path and operated each time a bent or curved portion of printing paper pushes the mechanical switch, and a counter for counting up operations of the mechanical switch, to judge whether or not the number of operations of the mechanical switch performed in a predetermined time exceeds a predetermined value, thereby checking whether or not the transporting path is jammed with the printing paper. Another conventional jam detecting device, as described in Japanese Patent Laid-open publication (JP-A) No. 60-35755, includes printing-paper detecting means provided at an appropriate position in a printing-paper transporting path, to judge that the transporting path is jammed with the printing paper, when the detecting means fails to detect the printing paper in a predetermine time.
In the above-mentioned jam detecting devices, when the printing-paper transporting path is blocked by the printing paper, or the printing paper is caught by something and thus is bent, the transporting path is judged to be jammed with the printing paper.
In a thermal ink-transfer printer, however, it is necessary not only to detect that the transporting path is jammed with the printing paper but also to detect if the transporting path is jammed with an ink donor sheet.
That is, in a thermal ink-transfer printer in which an ink donor sheet is placed on printing paper, and the ink on the ink donor sheet is transferred to the printing paper by supplying heat to the ink donor sheet, the ink donor sheet is put in close contact with the printing paper by a thermal head and a rotating drum. Accordingly, even after the ink transfer has been completed, the ink donor sheet is kept in close contact with the printing paper. When the separation of the ink donor sheet from the printing paper results in failure owing to static electricity or for other reasons, the ink donor sheet is drawn into a portion of a printing-paper transporting path, and thus there is a malfunction because the printing-paper transporting path is jammed with the ink donor sheet.